1. Field of the Invention
The present invention relates generally to an audio/video data synchronization apparatus for transmitting uncompressed audio/video data, and more particularly, to an audio/video data synchronization apparatus for directly transmitting decoded audio/video data to an external device, without compressing the data, by using Ultra-Wide Band (UWB) communication.
2. Description of the Related Art
In general, when a terminal transmits moving image data including large-capacity video data and audio data, the data is compressed before transmission by using moving image compression technology (e.g. MPEG or H.264). When a device receives the data, it decompresses the moving image data so that the video and audio data is output via a screen and a speaker, respectively. However, the receiving end of the device must incorporate a separate decoding function for decoding the compressed moving images. Furthermore, the video and audio qualities are usually worse than in the case of direct transmission of uncompressed video/audio data. Therefore, technology for directly transmitting audio/video data without compressing it when a terminal needs to transmit decoded audio/video data to an external device is needed.
In order to transmit large-capacity video/audio data wirelessly without compressing it, as mentioned above, wireless technology having a large transmission capacity is necessary, and UWB communication technology is drawing attention in this regard. The UWB communication technology refers to communication technology using a wide frequency band in a broad sense, and has mainly been under research for military purposes in the United States since the 1950s.
After declassification in 1994, several venture companies and laboratories started to develop the UWB wireless technology for commercial purposes. On Feb. 14, 2002, the U.S. Federal Communications Commission (the FCC) permitted commercial use of UWB wireless technology. Currently, IEEE (Institute of Electrical and Electronics Engineers) 802.15 WG (Working Group) is conducting standardization of the UWB technology. The FCC defines UWB as a type of wireless transmission technology using a frequency bandwidth of at least 20% with regard to the center frequency, or a bandwidth of 500 MHz or higher. The bandwidth is determined with regard to −10 dB threshold, not −3 dB threshold as in other types of communication. Unlike conventional narrowband communication for transmitting data by loading baseband signals onto carrier waves, UWB uses very short baseband pulses (i.e. nanosecond grade) so as to transmit data without using carrier waves. Particularly, UWB pulses correspond to several nanoseconds in the time-axis domain, and have a broad bandwidth (GHz grade) on the frequency spectrum. Therefore, it can be said that the UWB technology has a substantially broad frequency bandwidth compared with conventional narrowband wireless communication technologies. The UWB wireless technology, which uses very short pulses for data transmission, has several features distinguishing it from conventional narrowband communication. The UWB basically uses pulses for signal transmission and has a very broad bandwidth in the frequency domain, but a small transmission power density on the frequency axis. This means that communication is possible even below a noise band. Application fields of UWB communication include OFDM (Orthogonal Frequency Division Multiplexing). The OFDM transmission technology uses a number of multi-carriers so as to enable high-speed data transmission.
In general, when a terminal decodes moving image data for display, the data is divided into video and audio data, which are output via respective paths. Therefore, in order to directly transmit decoded video/audio data without compressing it, it is necessary not only to use a high data transmission rate, but also to synchronize the video and audio data, which are output via respective paths, according to the moving image playing time before transmission.